/**
 * Describes a problem that was encountered during settings building. A problem can either be an exception that was
 * thrown or a simple string message. In addition, a problem carries a hint about its source, e.g. the settings file
 * that exhibits the problem.
 */
class DefaultBuilderProblem implements BuilderProblem {
    final String source;
    final int lineNumber;
    final int columnNumber;

   *       threads, RPC network threads, or other latency-sensitive threads. In those cases, slow
   *       listeners can harm responsiveness, slow the system as a whole, or worse. (See also the
   *       note about locking below.)
   *   <li>If many tasks will be triggered by the same event, one heavyweight task may delay other
   *       tasks -- even tasks that are not themselves {@code directExecutor} tasks.

    @Nonnull
    Node collectDependencies(@Nonnull Project project);

    /**
     * Collects the transitive dependencies of some artifacts and builds a dependency graph. Note that this operation is
     * only concerned about determining the coordinates of the transitive dependencies and does not actually resolve the
     * artifact files.
     * <p>
     * Shortcut for {@code getService(DependencyCollector.class).resolve(...)}
     *

  //   completion preferably and AQS is non-deterministic (depends on where in the queue the waiter
  //   is). If we wanted to be strict about it, we could store the unpark() time in the Waiter node
  //   and we could use that to make a decision about whether or not we timed out prior to being
  //   unparked.

  /**
   * {@inheritDoc}
   *

     */
    /*
     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we
     * used Object[], we might be able to optimize toArray() to use clone() sometimes. (See
     * cl/592273615 and cl/592273683.)
     */

      Multiset<?> multisetToModify, Multiset<?> multisetToRetain) {
    return retainOccurrencesImpl(multisetToModify, multisetToRetain);
  }

  /** Delegate implementation which cares about the element type. */
  private static <E extends @Nullable Object> boolean retainOccurrencesImpl(
      Multiset<E> multisetToModify, Multiset<?> occurrencesToRetain) {
    checkNotNull(multisetToModify);

        K k = (K) key;
        return function.apply(k);
      } else {
        return null;
      }
    }

    @Override
    @CheckForNull
    public V remove(@CheckForNull Object key) {
      if (backingSet().remove(key)) {
        @SuppressWarnings("unchecked") // unsafe, but Javadoc warns about it
        K k = (K) key;